Shot blasting devices propel large volumes of abrasives at high velocity at workpieces in blast cabinets to effect cleaning of the workpieces for removing rust, paint and the like substances. De-greasing, etching, phosphating, rust-inhibiting and the like chemical treatments of workpieces normally must be effected by separate equipment through the spraying of a chemical solution at a workpiece in a wash cabinet. The shot blasting is affected in a separate cabinet.
U.S. Pat. No. 4,449,331 to MacMillan which issued May 22, 1984 discloses a shot blasting apparatus which includes a blast cabinet and an abrasive/contaminant separator and a conveyor. The workpiece is placed on a rotatable hanger within the blast cabinet to expose it to a cleaning stream of abrasive particles. In accordance with the method of this patent, the conveyor transmits spent abrasive and contaminants from the blast cabinet to a storage container. The conveyor is equipped so that it can handle both clean and spent abrasive simultaneously while keeping both separate. An air wash and sieves are utilized to separate contaminants from the abrasive.
U.S. Pat. No. 5,056,274 to Stem which issued Oct. 15, 1991 discloses the use of plastic granules within a liquid to form a slurry for propelling at a vehicle wheel for cleaning. Large particles that are loosened during the blasting process take part in the blasting along with the plastic granules.
U.S. Pat. No. 4,922,664 also discloses a liquid reclaim system whereby a liquid and abrasive mixture flows by gravity through a filtration system to separate the liquid and abrasive.
Discharge heads such as that disclosed in U.S. Pat. No. 4,907,379 to MacMillan which issued Mar. 13, 1990 propel abrasives at the workpiece. This patent discloses a one piece throwing wheel comprising a single side or back plate with angularly-spaced throwing blades for propelling shot at a workpiece.
U.S. Pat. No. 4,922,664 to Spinks et al which issued May 8, 1990 discloses a nozzle which contains a liquid supply means and an abrasive supply means. The liquid comes into contact with the abrasive within a chamber at an acute angle and propels the abrasive through an outlet bore to strike a workpiece. The optimum angle between the abrasive inlet and the liquid inlet is 30.degree.. The inlet bore of the liquid is co-axial with the outlet bore of the liquid and abrasive combination.
Cleaning of a workpiece by shot blasting and chemical treatment of a cleaned workpiece normally is effected by separate steps, thereby requiring a variety of relatively complex and expensive process equipment arranged in sequence and involving a time delay between cleaning and treatment steps during which the cleaned workpiece may oxidize or otherwise become contaminated. Abrasive material such as steel shot is heavier than the liquid in a shot/liquid slurry, the shot normally is discharged separate from the liquid off of the blades of a centrifugal impelling apparatus, thus impinging the shot on a workpiece in a different area than the area of impingement of the liquid.